Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
# -*- coding: utf-8 -*-
from collections import deque
h,w = map(int, input().split())
m = ["#"*(w+2)] + ["#"+input()+"#" for _ in range(h)] + ["#"*(w+2)]

cnt = 0
for hi in range(1,h+1):
    for wi in range(1,w+1):
        if m[hi][wi]==".":
            cnt += 1

inf = 10**9
d = [[inf]*(w+2) for _ in range(h+2)]
q = deque([(1,1,1)])
d[1][1] = 1
while len(q):
    ch,cw,r = q.popleft()

    for hi,wi in [[ch+1,cw],[ch,cw+1],[ch-1,cw],[ch,cw-1]]:
        if m[hi][wi]=="." and d[hi][wi]>r+1:
            d[hi][wi]=r+1
            q.append((hi,wi,r+1))

if d[h][w]==inf:
    print(-1)
else:
    print(cnt-d[h][w])